Conventionally, a diesel engine has a particular filter incorporated in an exhaust pipe for flow of exhaust gas to capture particulate matters or particulates in the exhaust gas. An oxidation catalyst having active species such as Pt or Pd is integrally carried by this kind of particulate filter for self-burning of the captured particulates even at a minimally low exhaust temperature.
However, a captured amount of particulates will exceed a treated amount of particulates in operation areas with low exhaust temperature levels. Continued operation with such low exhaust temperature levels may hinder sufficient regeneration of the particulate filter, resulting in excessive accumulation of the captured particulates in the particulate filter.
Conventionally proposed in this connection is to arrange a combustion appliance for raising the temperature of exhaust gas upstream of the particulate filter so as to introduce the exhaust gas produced by burner combustion and raised in temperature by the combustion appliance to the particulate filter and positively raise a catalyst bed temperature of the particulate filter and burn off the captured particulates, thereby regenerating the particulate filter.
There already exist, for example, the following Patent Literatures 1 and 2 as prior art documents on techniques for temperature raising of a particulate filter or the like by use of a burner.